Authors: Khokhlov V. M., Sirichenko K. S., Umanska O. V.
Cold spells (CS) are very important phenomena of European climate and have a significant impact on the environment and society. Cold spells are traditionally considered to be several consecutive days with the air temperature much lower than normal. The global climate change is revealed as increasing the various extreme weather phenomena, and there is an urgent need to study in detail these phenomena and to determine their variability. Typically, the CS is defined by using certain percentiles. It is advisable to use a 10th percentile and determine the rule – all the days with daily temperatures lower than 10th percentile are cold days. The cold spell is defined as at least three consecutive cold days. In this work, the calculation of 10th percentile was carried out for daily temperatures during the period from 1951 to 2010.
In general, the number of cold days for Ukraine is slightly more than 10% of the total number of calendar days, indicating a small asymmetry of statistical distribution. Nevertheless, it can be noted a sharp decrease in the total number of cold days eastward and northward of Central Ukraine. During the period of global cooling (1951-1980), the amount of cold days almost did not change from west to east of Ukraine, but in the following decades the cold days in eastern regions became lesser and lesser in comparison with the western regions. Finally, during the global warming, there was a significant reduction in cold days throughout Ukraine.
The greatest frequency of CSs is observed in western Ukraine, after which it sharply decreases, reaching the minimum in the eastern regions. The most prominent feature is the gradual increase in the annual number of CSs by about 1980 and their sharp decrease starting from the 1980 in all regions of Ukraine. Moreover, since 1998 the annual number of PCPs has not exceeded eight, and in 2007 the CSs have not been totally observed in the western and southern regions of Ukraine. This fact can be explained by the impact of global warming.
Only up 25% of all CSs were registered in the summer period. Such a small number of cold spells during the summer can be an indicator that the number of abnormally cold winters is significantly reduced during the period of global warming.
Tags: climate change; cold spells; temperature anomalies; Ukraine; аномалії температури; зміна клімату; періоди холодної погоди; Україна
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